1. Field of the Invention
The present invention relates to a snubber device which suppresses a surge voltage generated at a time of turn-off of a switching element or a reverse recovery of a diode used in an inverter or a chopper circuit, and also to a semiconductor device using the snubber device.
2. Description of the Background Art
In an inverter semiconductor module using a switching element having a high switching rate, such as an IGBT, a high voltage (turn-off surge voltage) is generated in floating inductance of a main circuit due to a rapid change of a current at a time of turn-off. At a time when a free-wheeling diode is turned off, a surge voltage (recovery surge voltage) is generated on the same principle.
Thereby, an external protection circuit (snubber device) which absorbs such a surge voltage is provided to a semiconductor module, to thereby suppress the surge voltage. In a typical basic configuration of the snubber device, a resistance R, a diode D, and a capacitor C are combined (for example, Japanese Patent Application Laid-Open No. 2010-115099), a resistance value and the capacitance of a capacitor are adjusted by wiring inductance of an application and the level of a drive current.
Although the external snubber device is an element necessary for a safe operation of a switching element, it is necessary to design heat dissipation of the snubber device itself, which increases the size as an application. Additionally, there is a problem of increased costs and efforts due to low-inductance wiring designing.